5691/6SL7GT RCA Red Base High Mu Twin Triode Tube. The red base 5691 is a premium 6SL7 made to last over 10,000 hours and produce low noise. We have a couple of
RCA 5691 Tube (New Old Stock In Pair) — Woo Audio
World's Best NOS 5691/6SL7 RCA Red Base Dual Triode Perfect Matched Pair
5691 RCA Red Base | TubeDepot.com
RCA 5691 Tube (New Old Stock In Pair) — Woo Audio
5691 RCA Red Base Black Plates NOS rebranded Westinghouse 1966